Geared rotary actuators of the conventional type used to position aircraft flight surfaces or the like are driven through drive shafts from a drive unit which is located at a position relatively remote from the surfaces to be positioned. Heretofore, conventional actuators have used central through shafts which are a permanent part of the actuator structure and which accept rotation from the drive shafting system and couplings to connect the systems to a gear reduction mechanism. Although these actuators do perform the needed positioning function, they are relatively complex, heavy and require extraneous components to support, locate and return the drive shafts and actuator shaft. Therefore, they tend to be more costly and less reliable.
In particular, actuator mechanisms have employed grounded ring gears with a center ring gear therebetween. A planet gear in the actuator housing would be arranged in meshing engagement with the center ring gear and with the end ring gears. A shaft journaled at each end in a housing was provided with a gear connected to the shaft either by being mounted on a splined section or cut directly into the shaft. Such an actuator is self-contained and will have a shaft with a spline on it so that a coupling can be put on it and drive off to the next actuator. Alternatively, it could have a female coupling. This type of arrangement required an independent external shaft which mounted in or to the internal shaft inside the actuator housing. However, this is a relatively complex arrangement in which the bearings used for the internal shaft serve no additional function.
It is also known to put journal bearings between the end ring gears and the center ring gear to keep the gears centered. Other arrangements have an axial bearing which requires additional structure to hold them together.
Furthermore, conventional actuators have used flanges at either or both ends of the central through-shaft so that a drive shaft can be bolted to the through shaft for operational purposes. Again, this arrangement makes the actuator more cumbersome and unnecessarily complicates installation of the actuator system.
All such prior actuators were unduly complex and heavy due to the presence of the central shaft and the need to connect a separate drive shaft to the actuator with consequent alignment problems.